Hypertension may be defined as a condition of sustained elevated arterial blood pressure, i.e., a diastolic pressure in excess of 90 mmHg. In the majority of cases, the patients are affected by essential hypertension, which by definition means that the underlying etiologic mechanism(s) is unknown. Regardless of the mechanism, a sustained elevation of blood pressure for a period of time has been shown to result in significant cardiovascular damage throughout the body, e.g., congestive heart failure, coronary artery disease, stroke and progressive renal failure [Veterans Administration Cooperative Study Group on Antihypertensive Agents: Effects of Treatment on Morbidity in Hypertension. Results in patients with diastolic blood pressures averaging 115 through 129 mm Hg, J.A.M.A., (1967), 202, 1028 and Veterans Administration Cooperative Study Group on Antihypertensive Agents: Effects of Treatment on Morbidity in Hypertension II. Results in patients with diastolic blood pressures averaging 90 through 114 mm Hg, J.A.M.A., (1970), 213, 1143].
The benefits of drug therapy to reduce and control blood pressure have been established [Woods, J. W., Current Therapy, ed. Conn, H.F., pp. 219-220, 1981]. Since the specific etiology is not usually known, an empirical approach to the treatment of hypertensive patients is taken. Often, the choice of treatment is based on the severity of the disease and the patient's response and compliance to initial therapy. The goal of the treatment is to reduce elevated blood pressure and maintain pressure at or near normal levels. An antihypertensive agent should be orally active and have a sufficiently prolonged duration of action to normalize hemodynamic derangements in humans.